Methods of making convergence cup electrodes by affixing shields to inner cylinder walls

ABSTRACT

Methods are disclosed for making cylindrical cup electrodes for three-gun color picture tubes having internally mounted shield inserts of magnetic material affixed to the inner walls of the cup. The upper rim of the cup is kept intact and may be flanged outwards to improve roundness after apertures are formed in the cup sidewalls. Apertures in the cup walls are confined to those required for magnetic pole pieces extending into said cup comprising three pairs of slits in the sidewalls of the cup.

United States Patent Inventor Jay H. Johnson Owensboro. Ky.

Filed Mar. 9. 1970 Division of Ser. No. 788,777. Jan. 3. 1969. Pat. No. 3.513.479, which is a continuationin-part of Ser. No. 633.822. -Apr. 26. 1967, Pat. No. 3.441.769

Patented July 20,1971

Assignee Kentucky Electronics, Inc.

Owensboro,.Ky.

METHODS OF MAKING CONVERGENCE CUP ELECTRODES BY AFFIXING SHIELDS T0 INNER CYLINDER WALLS 4 Claims, 1 Drawing Fig.

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[56] References Cited UNITED STATES PATENTS 2,991,381 7/1961 Hughes 3l3/70X 3,011,090 11/1961 3l3/70X 3,128,407 4/1964 313/82 3,322,990 5/1967 313/70 3,441,769 4/1969 313/84 3,513,479 5/1970 313/84 Primary Examiner-John F. Campbell Assistant Examiner-Richard Bernard Lazarus Att0rney- Laurence R. Brown ABSTRACT: Methods are disclosed for making cylindrical cup electrodes for three-gun color picture tubes having internally mounted shield inserts of magnetic material affixed to the inner walls of the cup. The upper rim of the cup is kept intact and may be flanged outwards to improve roundness after apertures are formed in the cup sidewalls. Apertures in the cup walls are confined to those required for magnetic pole pieces extending into said cup comprising three pairs of slits in the sidewalls of the cup.

PATENTEU JUL20 I97! 3, 593 396 INVENTOR JAY H. JOHNSON BY QQ M )l mw v) ATTORNEY METHODS OF MAKING CONVERGENCE CUP ELECTRODES BY AFFIXING SHIELDS T INNER" CYLINDER WALLS This application is a division of the copending application -Ser. No. 788,777 filed Jan. 3, 1969, now US. Pat. No.

3,513,479 issued May 19, 1970 which, inturn, is a continuation-in-part of application Ser. No. 633,822, filed Apr.- 26, 1967, now US. Pat. No. 3,441,769 issued on Apr. 29, 1969.

This invention relates to methodsofmaking electrodes'for controlling a beam within a cathodefray tube, and more par ticularly, it relates to a convergence cup electrode for three beam color television tubes. 1

Basically, this convergence .cup electrode is a cuplike 316C? trode of generally cylindrical shape of a thin-walled nonmagnetic metal. Inside the cup is a generally Y-shaped magnetic shield dividingthe interior of the cylinder into three-substantially equal compartments. A set of two magnetic polepieces protrude from the outside through two slots in each compartment to straddle an aperture in the closed cup bottom which passes an electron beam. Snubber springs are affixed to extend generally outwardly from the electrodeto press against the inside surface of the glass neckof the, cathode-ray tube for centering the gun therein. The pole pieces have flanges-adjacent the outer walls of the electrode and near the glass neck of the tube to communicate with convergence magnets located outside the tube envelope.

In constructing this convergence-cup assembly, great dif-' ficulty has been encountered in holding the roundness of theconvergence cup cylinder. It has been found that in punching rt six pole piece slots and three shield slots through the electrode walls, the cylindrical shape may be distorted out of tolerance.

It has been customary to nick orslot the top edge .of a con vergence cylinder at three positions about the'peripheryin 1. order to extend a flange on on the *Y-shaped-shields-through:

the cylinder walls for welding onto-theouter cylinder surface. This procedure has long been customary in commercial practice despite the many problems it produces. The cost and maintenance of dies that are needed to punch through stainless steel convergence cup walls, is significant. The punching technique is complicated seriously by the roundness of the walls that tends to deflect dies andmake precisepositioning of slots difficult, to say nothing of excessive die wear.

Furthermore, roundness acceptance tolerances of a convergence cup are strict, and any punching or slotting, particularly at the rim edge of a cup tends to misshape the cup and cause out of roundness. Also punched slots provide surfaces which: may develop burrs or sharp edges subject to corona discharge" and defective operation in the high-voltageenvironment of cathode-ray tube electrodes. Such slots areusually inaccessible to effective tumbling and deburring operations even if the cost of this additional step can be borne;

ln spite of all these deficiencies,cathode-ray tube color pic ture gun assemblies have for the past decade consistently mounted the V-shaped convergence shields -by extendingflanges through a slot in the cylinderwallsso that they could be welded on the outside of the cup. Perhaps in this critical'art subject to defect when a minor change is made that 'will'tend to disturb the electron beam characteristics or voltage distribution, there has been a reluctance to put a welded surface.

inside the electrode cup.

It is therefore an object of this invention to provide methods of making a convergence cup electrode structure resolving these deficiencies of the prior art.

Another object of the invention isto provide methods of making convergence cup electrodeassemblies while holding precise roundness tolerance during manufacture.

It has been discovered in accordance-with this invention that the convergence cup may be mademore precisely atless cost with structure successfully operating in the critical environment of a color picture tube gun exposed to high voltage for shaping, controlling and directing an electron beam with precision over a large range of conditions. Thus, the punched slots in the convergence cup atthe rim edge are avoided to thereby provide betterroundness of the convergence cup and to avoid problems causedby burrs and other distortions ofthe electric fieldconfiguration affecting the electron beam. Accordingly the V-shaped shield members are affixed to the inner'walls of the convergence cup cylinder with flanges abutting the walls near the rim at the open end of the cup. The abutted flanges are mounted in a position shielded from the electron beam by the magnetic convergence pole pieces to prevent 'anydanger of 'disto'rting'the beam with distorted inner cup wall surfaces caused by the welding or flange structure.

These and other aspects and objectives of the invention are related throughout the following detailed description which refers'to the'single FIGURE inthe accompanyingdrawing, which shows-a top view of a convergence cup assembly.

As seen from the drawing, the convergence cup may be a deep-drawn cylinder having a closed bottom 10. This cup has thin sidewalls of nonmagnetic metal such as'stainless steel and may have the upper rim '14 flangeoutwardly. Slots '15, 16 extend through the cup walls defining the limits of three separate compartments 18, 19, 20 through which an electron beam is passed.

Two magnetic pole pieces30, 31 extend through slots l5, 16 into each compartment l8, 19, 20 to straddle apertures 32, 33, 34which permit the three separate electron beams of a color picture tubeto pass through theconvergence cup electrode. The flanges 8 on the pole pieces 30, 31 abut the outer walls-of thecylinder to extend near the inner wall of the glass neck of the tube. about which a conventional convergence magnet array(not shown) is placed to communicate with the" pole pieces'30, 31 at each compartment.

ThreeV-shaped magnetic shield members 23, 24, and 25 extend radially from theircommon apex at the center 26 of the cupto the cylinderwalls forming three substantially-equal compartments in the cup to further-isolate the three beam compartmentswithin the convergence cup assembly. These shields 23,24,25 "are wholly contained within the cup and ex-' tend substantially'to the bottom of the 'cup. They are spot welded to the inner sidewalls of the cylinder near the upper rim 14 by means of flanges 21, 22 bent fromthe plane of each shield-to extend circumferentially adjacent the inner surface" 'of the cylinder toward the magnetic pole pieces 30, 31. Any

possible weld spots or disturbed magnetic or electric field patterns left inside the convergence cupby this mounting strue-' ture are'shielded from the beam, which passes through the apertures 32, 33 and '34, by means of the intervening pole pieces 30, 31.

Thus ithas been found in practice that this convergence cup positions for receiving therethrough to extend within the cylinder three pairs of magnetic convergence pole pieces straddling the path of each of said beams through said cylinder, while retaining the continuous upper rim intact and without substantially changing the roundness of said cylinder, and welding flange portions of magnetic convergence pole pieces to the cylinder exterior such that said pole pieces extend through the apertures into the cylinder, and

cylinder with flanges extending therefrom to fit circumferentially adjacent the inner cylinder walls, and

. forming a'set of magnetic shields to fltwholly within said e. welding said flanges to said cylinder to affix to the inner walls of said cylinder to extend wholly within said cylinder, said set of magnetic shields forming therewith three separate compartments respectively containing the pairs of said pole pieces.

2. The method defined in claim 1 including the step of flanging the upper rim of said cylinder outwardly before forming said apertures in said cylinder.

3. The method defined in claim 1 including the step of forming the flanged shield means of three V-shaped members.

4. The method of making a convergence cup electrode assembly for positioning in the neck portion of a three beam color television cathode ray tube comprising the steps of a. forming a hollow cylindrical thin walled cup with a closed bottom and open top with an upper rim thereabout forming anelectrode body of nonmagnetic material with three apertures defined in the closed bottom to pass said three beams and with a solid unapertured upper rim, said b. forming flanged shield means of magnetic material for fitting wholly within the cup to extend radially from a flange formed to conform adjacent the cylinder walls to the center of the cylinder to form three compartments encompassing the respective beam paths with the surrounding pair of convergence pole pieces, and

. affixing the shield means only to the inner walls of said cylinder by welding the flanges on the shield means to the inner walls at positions located between the pairs of pole pieces. 

1. The method of forming a convergence cup electrode for a three beam color tube comprising the steps of a. forming a cylinder of nonmagnetic metal with thin walls having a continuous open upper rim, b. forming in the walls of said cylinder, at a position intermediate the upper and lower rims, apertures located in positions for receiving therethrough to extend within the cylinder three pairs of magnetic convergence pole pieces straddling the path of each of said beams through said cylinder, while retaining the continuous upper rim intact and without substantially changing the roundness of said cylinder, and c. welding flange portions of magnetic convergence pole pieces to the cylinder exterior such that said pole pieces extend through the apertures into the cylinder, and d. forming a set of magnetic shields to fit wholly within said cylinder with flanges extending therefrom to fit circumferentially adjacent the inner cylinder walls, and e. welding said flanges to said cylinder to affix to the inner walls of said cylinder to extend wholly within said cylinder, said set of magnetic shields forming therewith three separate compartments respectively containing the pairs of said pole pieces.
 2. The method defined in claim 1 including the step of flanging the upper rim of said cylinder outwardly before forming said apertures in said cylinder.
 3. The method defined in claim 1 including the step of forming the flanged shield means of three V-shaped members.
 4. The method of making a convergence cup electrode assembly for positioning in the neck portion of a three beam color television cathode ray tube comprising the steps of a. forming a hollow cylindrical thin walled cup with a closed bottom and open top with an upper rim thereabout forming an electrode body of nonmagnetic material with three apertures defined in the closed bottom to pass said three beams and with a solid unapertured upper rim, said cylinder having only one set of three pairs of slots provided in the cylinder walls receiving and positioning magnetic convergence pole pieces on either side of each of said apertures in the bottom to permit the three beams to pass through the cup in a substantially axial path, between said pole pairs, b. forming flanged shield means of magnetic material for fitting wholly within the cup to extend radially from a flange formed to conform adjacent the cylinder walls to the center of the cylinder to form three compartments encompassing the respective beam paths with the surrounding pair of convergence pole pieces, and c. affixing the shield means only to the inner walls of said cylinder by welding the flanges on the shield means to the inner walls at positions located between the pairs of pole pieces. 